bad Earth? got some readings of current drain

[bad_religion_au]

problem started when i was trying to start, no starter motor at all, just a sick click.

roll started it, ran fine, but every time brake lights or indicators were put on, the car stereo stopped, and when i put the headlights on, the motor died in the ass, lights off, travel fine...

still no starter motor

[murcod]

Check your positive and negative cables at the battery and your negative where it bolts onto the engine and chassis.

Look for broken wires at the terminals, corrosion where they bolt onto the chassis etc. Check the battery voltage with a multimeter- should be around 12.5V while not cranking; high 13V while motor is running.

Do any of the cables get hot when you're trying to start it?

Also check your ignition switch and any fuses/ fusible links for breakages and corrosion (and any plugs/ connectors.)

That should keep you busy for a while!

[-Scott-]

Yep - I'm with murcod.

I'd suspect the earth connection between engine and chassis/battery. If that's picked up extra resistance it may be that enough current flows to pull in the solenoid on the starter, but it's too much resistance to allow full started current. Measure voltage between block and negative terminal while you're trying to start - without the starter turning it should be well under a volt.

I'm guessing wherever the bad connection is, headlight current flows through it too - turn your headlights on and enough voltage drop is created to kill your ignition.

It's a good one!

Good luck,

Scott

[bad_religion_au]

cleaned up all the terminals, it cranked fine and ran fine, then the battery crapped out, seems to crank fine now with the battery out of another car (for how long is another question, that battery has started going flat in the other car).

looks like i'm in the market for two new 4x4 batteries, hopefully crappy connection terminals was all the problem was.

yes the terminals got extremely hot when trying to crank it b4 the cleanup, what does that tell us???

[-Scott-]

yes the terminals got extremely hot when trying to crank it b4 the cleanup, what does that tell us???

The heat is caused by dissipation of power in a resistance. The resistance was the dirty terminals. Clean terminals = very low resistance = much less power dissipation.

Cheers,

Scott

[murcod]

Heat in a cable under load indicates resistance in that area.

[bad_religion_au]

ok got a new battery in one (of two that are buggered) of the cars, tested current between -ve terminal on the battery, and the negative wire going to the battery, started pulling fuses to find the drain on the battery

there is a 0.1 milliamp drain in the taillight circuit

the hard wire circuit that keeps the cd player memory and clock etc draws over 200 milliamps, but that fluctuates down to 4-5 milliamps at times.

i don't know what current draw is alright for automotive sources, is 200 milliamps too high?

is the .1 milliamp draw a huge problem (i.e. could it be causing the battery drain in less than a day?)

[Adomw]

Mate it's all about amp hours

if you have a 100AH battery( roughly standard for big 4X4) then you can draw 1 amp for 100 hours (all things being equal) or 20A for 5 hours etc - you do the maths

so theoretically if you have a 200ma drain it would take 500hours to flatten the above battery

if you are worried about things like clocks, alarms flattening your battery then disconnect one terminal from your battey and set your multimeter to the 20A (to start with) setting and make the connection between the battery and the cable with the mulimeter and read it off. you shouldn't have more than about 1A or 1000ma draw with everything switched off.

if you have more than that draw then start pulling the fuses to the ancillary devices like clocks, car radios etc until you identify which piece of gear is draining

if you find that it's none of these sevices then suspect a blown diode or some such in the alternator - even the starter motor soliniod can cause a drain

[murcod]

there is a 0.1 milliamp drain in the taillight circuit

the hard wire circuit that keeps the cd player memory and clock etc draws over 200 milliamps, but that fluctuates down to 4-5 milliamps at times.

i don't know what current draw is alright for automotive sources, is 200 milliamps too high?

is the .1 milliamp draw a huge problem (i.e. could it be causing the battery drain in less than a day?)

Is that 0.1mA (0.0001A) or 0.1A you've got in the tail light circuit?? One is stuff all and not worth worrying about- the other is a concern!

The memory circuit for your stereo etc should sit at around 4-5mA- it shouldn't be getting up to 200mA. Try isolating it further to work out what is causing it to rise to 200mA.

[bad_religion_au]

Is that 0.1mA (0.0001A) or 0.1A you've got in the tail light circuit?? One is stuff all and not worth worrying about- the other is a concern!

The memory circuit for your stereo etc should sit at around 4-5mA- it shouldn't be getting up to 200mA. Try isolating it further to work out what is causing it to rise to 200mA.

it is 0.1mA, so i guess nothing to worry about.

how would i seperate the stereo memory circuit further? the setup i run is the hot wire specified in the head unit instructions to the battery through a fuse. i can't think of what to seperate further (but hey i only bought my first ammeter today, so i'm new at this). i seperated that circuit by pulling the fuse.

as i said, it was a bit strange, cause it would sit at a little higher than 200 milliamps, then drop to 2.5 milliamps, then back up.

it's an interesting problem, the battery only drains say once a month, jump start it, run it on the highway, it's fine, till next month, so i guess that means my alternator is working.

if i broke the circuit at the -ve terminal, put my ammeter into the circuit there, this would show me if the starter solinoid was shot wouldn't it?

[murcod]

So it's only your CD player that draws the 200mA? I misread it earlier and thought a (separate?) clock was included in that reading?

That's a lot of current to have being continually drained- I'd suggest there's something wrong with it. You should only have around 1/10th of that being drained for everything (including an alarm if you've got one fitted.)

[bad_religion_au]

sorry, wasn't too clear, i meant the clock that is part of the head unit.



can't think why it's draining so much juice to store the memory settings, it is on it's own circuit, goes +ve terminal, fuse holder (those little round screw top ones with glass fuses) memory circuit on head unit, earthed under the dash...

any suggestions